It is well known to provide a loudspeaker unit which includes two or more individual speakers (also known as drivers) to cover different sections of the frequency spectrum. Loudspeakers with multiple drivers are desirable because a single driver large enough to provide adequate response at low frequencies is not capable of providing an adequate response at higher frequencies. Such systems are commonly known as two or three way systems, depending upon whether a separate driver is provided to cover two or three different frequency portions, respectively.
Moreover, in some known designs where higher efficiency is a concern, multiple drivers may be provided in each crossover section or for each frequency band. It is not uncommon to have up to three drivers or speakers in a low pass section and even two drivers in a midrange section.
A disadvantage to a loudspeaker having multiple drivers is that the drivers occupy more space, and can narrow the spatial characteristics of the system. For example, the sound from multiple speakers or drivers can appear to be more directional than from a single driver. This effect is more pronounced at higher frequencies.
One known technique for reducing this disadvantage of multiple drivers is to differentiate the signals fed to the individual drivers in one section. This is achieved by setting different low pass cutoff frequencies for each driver and this is common practice where multiple drivers are provided. The effect of this technique is to reduce the number of drivers participating in sound reproduction at higher frequencies, thereby improving sound dispersion.
However, this technique has a number of disadvantages. One of the disadvantages is lower efficiency, since at higher frequencies fewer drivers are radiating the sound. Another disadvantage is that is difficult to achieve a flat frequency response, because of a complex phase relationship between drivers connected to different low pass filters. Even if systems employing low pass filters are designed, using simple mathematical addition, to produce a flat frequency response, in practice, such systems often introduce unwanted and varying phase shifts. At higher frequencies, these phase shifts can be even more pronounced, and, result in a reduced signal level.
Accordingly, there is a need for a loudspeaker system to simply and efficiently distribute an input signal between a number of drivers. There is a further need for a system which enables different low pass cut off frequencies to be set for the drivers, while enabling a more flat, total frequency response to be provided.